www/typo3: Update from 7.6.14 to 7.6.15

Changelog: https://wiki.typo3.org/TYPO3_CMS_7.6.15

This fixes also a security issue with the mailtransport.

PR: 215756
Submitted by: Jochen Neumeister <joneum@bsdproject.de>
Reviewed by: freebsd-ports@charlieroot.de (maintainer)
MFH: 2017Q1